Influence of coal reservoir fracture pressure on fracturing reconstruction and its engineering application

Abstract

The permeability of coal reservoirs in China is generally low, and the benefit of direct development of surface coalbed methane in low permeability reservoirs is low, and hydraulic fracturing is an effective means to increase the permeability and conductivity of coal reservoirs. Based on the analysis of logging parameters of well PN-1 and well PN-2 in Qinshui Basin, the rock mechanics characteristics of coal reservoir are mastered, which provides guidance for the optimization of hydraulic fracturing parameters of coal reservoir. The results show that the coal seam derived from the logging data of the two wells has the characteristics of low Poisson’s ratio, low Young’s modulus, low strength and low rupture pressure. By controlling the construction displacement and pressure and increasing the liquid volume in the pre-liquid phase, the fracturing fracture can be effectively prevented from extending along the interlayer interface between the top and bottom of the coal seam and extending to the top and bottom of the coal seam. The fracture pressure of coal seam in well PN-1 obtained from logging data is close to the actual fracturing pressure, and the error is only 3.01%, which has a high guiding significance for the optimization of fracturing construction parameters. The fracturing pressure of the coal seam in well PN-2 is slightly lower than that of the top and bottom rock, and the construction displacement in the initial stage of fracturing is high, resulting in the construction pressure reaching the fracturing pressure of the top and bottom, and the fracturing fracture extends between the top and bottom to form a single fracture, resulting in poor transformation effect and gas production effect.

Keywords

• gas drainage
• coal reservoir
• rupture pressure
• hydraulic fracturing
• compressibility
• transformation effect